Les nouveaux neurones de l’hippocampe semblent contribuer à l’action thérapeutique des antidépresseurs. La nature fonctionnelle de cette contribution est cependant inconnue. En stimulant la neurogenèse les antidépresseurs pourraient renforcer certaines fonctions de l’hippocampe et ainsi permettre la rémission. Nous montrons dans ce travail que les nouveaux neurones peuvent contribuer à l’action thérapeutique des antidépresseurs en participant au renforcement de rétrocontrôle hippocampique sur la régulation de l’axe HPA, potentiellement via leur rôle dans la capacité de l’hippocampe à moduler l’activité des autres structures impliquées dans la régulation du stress, comme le noyau du lit de la strie terminale. Les différentes composantes fonctionnelles de l’hippocampe sont cependant topographiquement distribuées le long de son axe septo-temporal. A travers une approche corrélative nous avons montré que différents antidépresseurs régulent la neurogenèse différentiellement le long de l’axe septo-temporal. Cela suggère des mécanismes de régulation régiondépendants et que la contribution des nouveaux neurones dans les effets des antidépresseurs pourrait être multiple et sous tendue par des composantes fonctionnelles différentes, et non limitée à la régulation de l’axe du stress. / Hippocampal newborn neurons contribute to some extent to the therapeutic effects of antidepressants. Mechanisms involved in this contribution remain however elusive. By increasing the recruitment of newborn neurons antidepressants could improve several hippocampal functions and thus allow remission. Here we demonstrate that newborn neurons may contribute to the therapeutic effects of antidepressants by allowing the recovery of a proper hippocampal inhibitory feedback over the HPA axis, possibly by normalizing the communication between the hippocampus and stress integrative structures mediating its inhibitory influence, such as the bed nucleus of the stria terminalis. Hippocampal functions are however topographically segregated along its septo-temporal axis. Here we show that different mood-improving manipulations differentially regulate neurogenesis along this septo-temporal axis. This suggest different region-specific mechanisms involved in the regulation of neurogenesis and that newborn neurons may contribute to the therapeutic effects of antidepressants by modulating different aspects of hippocampal functions.

O neuropeptídeo/hormônio CRF integra respostas de estresse a nível endócrino, imunológico e comportamental dos mamíferos. A atividade neuronal CRFérgica inapropriada pode estar por trás do aparecimento de sintomas associados a transtornos neuropsiquiátricos. Os experimentos apresentados nesta tese descrevem a modulação farmacológica de ligantes de CRF que compõem o sistema CRFérgico em ratos Wistar machos submetidos ao protocolo de estresse por derrota social. A experiência de episódios intermitentes à derrota social prejudicou o comportamento de interação social. Microinjeções de antagonista da proteína ligante de CRF e antagonista (CRF6-33) e antagonista específico do receptor de CRF do tipo 1 (CP316311) no núcleo intersticial da estria terminal, separadamente, restauraram a aproximação social em animais estressados. Esses achados sugerem que o conteúdo de CRF no núcleo intersticial da estria terminal está envolvido na modulação de respostas relacionadas à ansiedade induzidas pelo estresse social. / The CRF neuropeptide/hormone integrates endocrine, immune and behavioral stress responses of mammals. Inappropriate CRFergic neuronal activity may underlie the appearance of symptoms associated with neuropsychiatric disorders. The experiments presented in this dissertation describe the pharmacological modulation of CRF ligands composing the CRFergic system in male Wistar rats submitted to the social defeat stress protocol. The experience of intermittent episodes of social defeat disrupted behaviors of social interaction. Microinjections of an antagonist of CRF binding protein (CRF6-33) and specific antagonist of CRF receptor type 1 (CP316311) in the bed nucleus of stria terminalis, separately, restored the social approach behavior in stressed animals. These findings suggest that the CRF content in the bed nucleus of stria terminalis is involved in the modulation of anxiety-related responses induced by social stress.

O neuropeptídeo/hormônio CRF integra respostas de estresse a nível endócrino, imunológico e comportamental dos mamíferos. A atividade neuronal CRFérgica inapropriada pode estar por trás do aparecimento de sintomas associados a transtornos neuropsiquiátricos. Os experimentos apresentados nesta tese descrevem a modulação farmacológica de ligantes de CRF que compõem o sistema CRFérgico em ratos Wistar machos submetidos ao protocolo de estresse por derrota social. A experiência de episódios intermitentes à derrota social prejudicou o comportamento de interação social. Microinjeções de antagonista da proteína ligante de CRF e antagonista (CRF6-33) e antagonista específico do receptor de CRF do tipo 1 (CP316311) no núcleo intersticial da estria terminal, separadamente, restauraram a aproximação social em animais estressados. Esses achados sugerem que o conteúdo de CRF no núcleo intersticial da estria terminal está envolvido na modulação de respostas relacionadas à ansiedade induzidas pelo estresse social. / The CRF neuropeptide/hormone integrates endocrine, immune and behavioral stress responses of mammals. Inappropriate CRFergic neuronal activity may underlie the appearance of symptoms associated with neuropsychiatric disorders. The experiments presented in this dissertation describe the pharmacological modulation of CRF ligands composing the CRFergic system in male Wistar rats submitted to the social defeat stress protocol. The experience of intermittent episodes of social defeat disrupted behaviors of social interaction. Microinjections of an antagonist of CRF binding protein (CRF6-33) and specific antagonist of CRF receptor type 1 (CP316311) in the bed nucleus of stria terminalis, separately, restored the social approach behavior in stressed animals. These findings suggest that the CRF content in the bed nucleus of stria terminalis is involved in the modulation of anxiety-related responses induced by social stress.

O neuropeptídeo/hormônio CRF integra respostas de estresse a nível endócrino, imunológico e comportamental dos mamíferos. A atividade neuronal CRFérgica inapropriada pode estar por trás do aparecimento de sintomas associados a transtornos neuropsiquiátricos. Os experimentos apresentados nesta tese descrevem a modulação farmacológica de ligantes de CRF que compõem o sistema CRFérgico em ratos Wistar machos submetidos ao protocolo de estresse por derrota social. A experiência de episódios intermitentes à derrota social prejudicou o comportamento de interação social. Microinjeções de antagonista da proteína ligante de CRF e antagonista (CRF6-33) e antagonista específico do receptor de CRF do tipo 1 (CP316311) no núcleo intersticial da estria terminal, separadamente, restauraram a aproximação social em animais estressados. Esses achados sugerem que o conteúdo de CRF no núcleo intersticial da estria terminal está envolvido na modulação de respostas relacionadas à ansiedade induzidas pelo estresse social. / The CRF neuropeptide/hormone integrates endocrine, immune and behavioral stress responses of mammals. Inappropriate CRFergic neuronal activity may underlie the appearance of symptoms associated with neuropsychiatric disorders. The experiments presented in this dissertation describe the pharmacological modulation of CRF ligands composing the CRFergic system in male Wistar rats submitted to the social defeat stress protocol. The experience of intermittent episodes of social defeat disrupted behaviors of social interaction. Microinjections of an antagonist of CRF binding protein (CRF6-33) and specific antagonist of CRF receptor type 1 (CP316311) in the bed nucleus of stria terminalis, separately, restored the social approach behavior in stressed animals. These findings suggest that the CRF content in the bed nucleus of stria terminalis is involved in the modulation of anxiety-related responses induced by social stress.

博士(理学) / Doctor of Philosophy in Science / 同志社大学 / Doshisha University

L'amygdale centrale (EAc) est un macrosystème du cerveau antérieur qui joue un rôle important dans la peur, l'anxiété et la douleur. Les deux composants clés, le noyau latéral du lit de la strie terminale (STL) et l’amygdale centrale (CeA), possèdent des caractéristiques neurochimiques, hodologiques et fonctionnelles très similaires. En dépit de cette vision simplifiée du STL et du CeA, de nombreuses questions résident quant à l'organisation mésoscopique des entrées et des sorties des subdivisions de l''EAc chez la souris. En outre, il reste à déterminer si ces similitudes de connexion sont également partagées au niveau cellulaire. Dans ce travail, nous avons abordé ces questions de manière comparative chez la souris. Nous avons trouvé de riches afférences et efférences préférentielles pour les différentes subdivisions de l'EAC, ainsi que des afférences convergentes et divergentes. Nous avons également mis en évidence deux groupes distincts de cellules exprimant la protéine kinase C delta (PKCδ) ou la somatostatine (SOM) qui sous-tendent des circuits neuronaux spécifiques parallèles dans le STL et le CeA, ainsi qu'entre les deux structures. Enfin, des données préliminaires suggèrent que les neurones exprimant la PKCδ dans le STL et le CeA pourraient être impliqués dans la douleur tonique. Ces organisations structurales parallèles, mais aussi différentielles, des circuits neuronaux dans le EAc pourraient sous-tendre des aspects fonctionnels similaires et dissociables de l'anxiété, de la peur et de la douleur. / Central extended amygdala (EAc) is a forebrain macrosystem that plays important roles in fear, anxiety and pain. The two key components, the lateral bed nucleus of stria terminalis (STL) and central nucleus of amygdala (CeA), are highly similar in their neurochemical, connectional, and functional features. Despite this simplified view of STL and CeA, much remains elusive of the mesoscopic inputs and outputs of EAc subdivisions in mouse model. Also, it is not known whether the connectional similarities are also shared at cellular level. Here, we addressed these question in comparative ways in mice. We found rich preferential inputs and outputs to different subdivisions of EAc, as well as convergent and divergent inputs. We also found two non-overlapping cell groups expressing either protein kinase C delta (PKCδ) or somatostatin (SOM) organize the parallel cell-type specific neuronal circuits in STL and CeA. Finally, preliminary data suggest that PKCδ in STL and CeA might be implicated in tonic pain. These parallel but also differential structural organizations of neuronal circuits in EAc might underlie similar and dissociable functional aspects of anxiety, fear and pain.

No description available.

La prise volontaire de nicotine augmente l'excitabilité de la voie ILCx-BNST, entraînant une hyperactivité des neurones DA de l’ATV. Dans une première partie, l'objectif était d’étudier les neuroadaptations de la voie ILCx-BNST induites par l'auto-administration intraveineuse (AAIV) de nicotine. Les récepteurs cannabinoides CB1 contrôlent les propriétés renforçantes de la nicotine. Par conséquent, nous avons examiné le rôle des récepteurs CB1 du BNST. Nous montrons que l'acquisition de l’AAIV de nicotine est associée à une facilitation persistante de l'induction d’une potentialisation à long terme (LTP) CB1-dépendantes des synapses ILCx-BNST. La stimulation électrique du ILCx favorise également la persistance du comportement de recherche de nicotine pendant les périodes où la drogue n'est pas disponible. En outre, en utilisant la pharmacologie intra-BNST, nous montrons que la stimulation des récepteurs CB1 du BNST au cours de l’acquisition de lAAIV augmente la sensibilité aux stimuli associés à la nicotine. L’idée qu’il existe un appétit incontrôlable pour les aliments palatables, en dépit des conséquences négatives. Dans une seconde partie, notre projet a porté sur le rôle des neurones dopaminergiques (DA) de l’ATV dans la perception d’un stimulus aversif chez l’animal exposé au sucrose. Nos résultats indiquent que le sucrose augmente l'activité spontanée des neurones DA de la VTA. En outre, si un choc électrique provoque une inhibition presque complète de l'activité de VTA neurones DA chez les rats témoins, le sucrose perturbe la signalisation d'un stimulus aversif, indépendamment de l’état calorique du rat. / Learning mechanisms associated with active responding for nicotine enhanced the excitability of the ILCx-BNST pathway. The objective of this project was to better understand the involvement of the ILCx-BNST pathway in nicotine self-administration. Since the endocannabinoid system controls nicotine reinforcement and nicotine-induced synaptic modifications, we examined the role of CB1 receptors in the BNST. We showed that acquisition of nicotine IVSA was associated with a persistent facilitation of LTP induction at ILCx-BNST synapses. Behaviorally, electrical stimulation temporarily increased excessive responding to nicotine when nicotine was not available. Moreover, using intra-BNST pharmacology, we revealed that stimulation of BNST CB1 receptors enhanced sensitivity to nicotine-paired cue. In contrast, after a prolonged history of nicotine intake, it blocked drug-seeking in a reinstatement model of relapse. Drug addiction is partly due to the inability to stop using despite negative consequences. The hypothesis that palatable food induces similar uncontrolled consumption is becoming more widespread. As drug addiction is known to increases activity of VTA DA neurons, we aimed to examine whether exposure to sucrose would induce similar neuronal modifications and impair the capacity to respond to an aversive stimulus. We found that sucrose enhanced spontaneous activity of DA VTA neurons. In addition, while a footshock caused a nearly complete inhibition of activity of VTA DA neurons in control rats, sucrose disrupted signaling of an aversive stimulus. These modifications were independent from the caloric state of the rats.

Les neurones dopaminergiques (DA) de l’aire tegmentale ventrale (VTA) sont influencés par différents stimuli comme des récompenses naturelles et d’autres stimuli moins physiologiques tels que les drogues d’abus. Ces drogues agissent en détournant les mécanismes d’apprentissage qui sous-tendent normalement la motivation pour des renforçateurs naturels. Les neurones DA, en conditions physiologiques, sont subtilement régulés par une balance entre tonus GABA et glutamatergique. Ils sont soumis à de multiples sources inhibitrices dont le noyau accumbens, les interneurones locaux ou les neurones GABA de la queue de la VTA (tVTA). Le glutamate est également important dans leur modulation. Il contrôle leur activité en bursts, qui est le mode de décharge le plus efficace pour libérer de la dopamine et coder des informations associées à la récompense. Il permet des adaptations synaptiques à long terme qui se sont révélées importantes dans la prise de drogue. La connaissance des facteurs endogènes qui contrôlent l’excitabilité des cellules DA de la VTA est essentielle à la compréhension des processus physiologiques (recherche de plaisir…) mais aussi pathologiques (addiction…). L’objectif de mon travail a été de comprendre les circuits de régulation des neurones DA en conditions physiologiques et lors de l’exposition à la morphine. Dans un premier temps, nous avons étudié les mécanismes de régulation des neurones DA par la formation hippocampique ventrale incluant le subiculum ventral et l’aire CA1 ventrale (vSUB/CA1). Grâce à l’utilisation d’approches d’électrophysiologie in vivo chez le rat anesthésié, nous avons montré que le vSUB/CA1 exerce un contrôle excitateur glutamatergique des neurones DA. Nous avons mis en évidence que cette voie vSUB/CA1-VTA est polysynaptique, faisant intervenir le BNST comme relais. J’ai aussi pu confirmer le rôle fonctionnel de la tVTA en tant que nouvelle structure GABA modulant l’activité des neurones DA, renforçant ainsi l’idée d’une balance entre tonus GABA et glutamatergique régulant les neurones DA in vivo.La deuxième partie de ma thèse a consisté en l’étude des circuits neuronaux à l’origine des effets excitateurs de la morphine sur les neurones DA de la VTA in vivo. L’hypothèse actuelle est que la morphine excite les neurones DA par un mécanisme de désinhibition en inhibant les neurones GABA de la VTA. Grâce à l’utilisation d’approches multiples, nous avons proposé un nouveau circuit expliquant les effets de la morphine. Ces effets sont la conséquence d’une modification de la balance GABA/glutamate par la morphine. Elle se traduit par une diminution du tonus GABA et d’une augmentation du tonus glutamatergique. Enfin, nous avons pu démontrer qu’une seule exposition à la cocaïne augmente l’activité de base des neurones DA. Chez ces animaux, les effets excitateurs de la morphine sont potentialisés confirmant ainsi l’hypothèse que l’amplitude de l’activation des neurones DA par la morphine dépend de leur état d’excitabilité. / Dopaminergic (DA) neurons of the ventral tegmental area (VTA) are influenced by several stimuli such as natural rewards or drugs of abuse. Drugs shunt learning mechanisms which underlie motivation for natural reinforcers. Under physiological conditions, DA neurons are regulated by a balance between GABA and glutamatergic inputs. They receive several inhibitory inputs especially from the nucleus accumbens, VTA local interneurons and GABA neurons of the tail of the VTA (tVTA). Glutamate is also important in modulating DA neuron activity. It controls their bursting activity which is the most efficient way to release dopamine and to encode reward-associated informations. It allows long term synaptic adaptations important for addiction. Knowing how these endogenous factors control VTA DA neuron excitability is essential to understand physiological (search for pleasure…) and pathological (drug addiction…) processes.In the first part of my thesis, we studied the regulation of the VTA by the hippocampal formation including the ventral subiculum and the ventral CA1 area (vSUB/CA1). Using electrophysiological approaches in anesthetized animal, we showed that the vSUB/CA1 controls VTA DA neurons and that this input is glutamatergic. We also demonstrated that the vSUB/CA1-VTA pathway is polysynaptic implicating the BNST as a relay. I also confirmed the inhibitory control of the VTA by tVTA, new GABA input to DA neurons. Thus, in vivo, DA neurons are regulated by a balance between GABA and glutamatergic inputs. The second part of my research consisted in studying the neuronal circuits underlying excitatory effects of morphine on VTA DA neurons in vivo. The actual hypothesis is that morphine excites DA neurons by a disinhibition mechanism inhibiting VTA GABA neurons. Using several approaches (electrophysiological approaches in anesthetized animal, tract-tracing methods), we proposed a new circuitry explaining morphine effects. These excitatory effects result from a modification of the balance between GABA and glutamatergic inputs with a decrease of the GABA tone and an increase of the glutamatergic tone. Finally, we demonstrated that an acute cocaine exposure increases DA neuron activity. In animals exposed to cocaine, morphine excitatory effects are potentiated. This last experiment confirms the hypothesis that the amplitude of morphine-induced activation of VTA DA neurons depends on their excitability state.

Ciliary neurotrophic factor (CNTF) is produced by astrocytes which have been implicated in regulating stress responses. We found that CNTF in the medial amygdala (MeA) promotes despair or passive coping, i.e., immobility in an acute forced swim stress, in female mice, while having no effect in males. Neutralizing CNTF antibody injected into the MeA of wildtype females reduced activation of downstream STAT3 (Y705) 24 and 48 h later. In concert, the antibody reduced immobility in the swim test in females and only after MeA injection, but not when injected in the central or basolateral amygdala. Antibody injected into the male MeA did not affect immobility. These data reveal a unique role of CNTF in female MeA in promoting despair or passive coping behavior. Moreover, 4 weeks of chronic unpredictable stress (CUS) increased immobility in the swim test and reduced sucrose preference in wildtype CNTF+/+, but not CNTF-/- littermate, females. Following CUS, 10 min of restraint stress increased plasma corticosterone levels only in CNTF+/+ females. In males, the CUS effects were present in both genotypes. Further, CUS increased CNTF expression in the MeA of female, but not male, mice. CUS did not alter CNTF in the female hippocampus, hypothalamus and bed nucleus of stria terminalis. This suggests that MeA CNTF has a female-specific role in promoting CUS-induced despair or passive coping, behavioral anhedonia and neuroendocrine responses. Compared to CNTF+/+ mice, CNTF-/- mice did not show differences in CUS-induced anxiety-like behavior and sensorimotor gating function as measured by elevated T-Maze, open field and pre-pulse inhibition of the acoustic startle response. Together, this study reveals a novel CNTF-mediated female-specific mechanism in stress responses and points to opportunities for developing treatments for stress-related disorders in women.